Various methods are known in the art for optical 3D mapping, i.e., generating a 3D profile of the surface of an object by processing optical radiation received from the object. This sort of 3D profile is also referred to as a 3D map, depth map or depth image, and 3D mapping is also referred to as depth mapping. “Optical radiation” includes any and all electromagnetic radiation in the visible, infrared and ultraviolet portions of the spectrum.
Some 3D mapping techniques are based on measurement of the time of flight of optical pulses. For example, U.S. Patent Application Publication 2013/0207970, whose disclosure is incorporated herein by reference, describes a scanning depth engine, in which mapping apparatus includes a transmitter, which emits a beam comprising pulses of light, and a scanner, which is configured to scan the beam, within a predefined scan range, over a scene. A receiver receives the light reflected from the scene and generates an output indicative of a time of flight of the pulses to and from points in the scene. A processor is coupled to control the scanner so as to cause the beam to scan over a selected window within the scan range and to process the output of the receiver so as to generate a 3D map of a part of the scene that is within the selected window.
In some cases, the same scanner can be used for both 3D mapping and projection of visible light. For example, U.S. Pat. No. 9,098,931, whose disclosure is incorporated herein by reference, describes apparatus for mapping that includes an illumination module, which includes a radiation source, which is configured to emit a beam of radiation. A scanner receives and scans the beam over a selected angular range. Illumination optics project the scanned beam so as to create a pattern of spots extending over a region of interest. An imaging module captures an image of the pattern that is projected onto an object in the region of interest. A processor processes the image in order to construct a three-dimensional map of the object.
In one of the embodiments described in U.S. Pat. No. 9,098,931, the radiation source includes a first radiation source, which emits an infrared beam, which is modulated to create the pattern of the spots, and a second radiation source, which emits a visible light beam, which is modulated to project a visible image onto the region of interest. The scanner and optics are configured to project both the infrared beam and the visible light beam onto the region of interest simultaneously. Typically, the second radiation source is controlled so as to project the visible image onto the object responsively to the 3D map.